6G2 STATE BOARD OF AGRICULTURE. 



The foregoing tables and charts show many extremely interesting 

 facts. Considering first the rate of freezing it will be seen that the sand 

 treated with the different solutions and with pure water cooled at about 

 the same rate until the temperature of about ?>4:° F. was reached when 

 the rate of falling of temperature of the sand treated with the water 

 slowed up while the temperature of the sand treated with the solutions 

 continued to fall until the respective freezing points were reached. The 

 sand, therefore, treated with the solutions came to the temperature of 

 32° F. about 15 minutes before did the sand treated with water. The 

 freezing point of the sand with the different treatments is markedly dif- 

 ferent; that with water is 31.8°., that with 0.5, 1.0 and 1.5 normal solu- 

 tions of KCl is 28.8°, 25.0° and 20.8° respectively, while that with 0.5 

 1.0 and 1.5 normal solutions of NH^Cl is 28.4, 25, and 22° respectively. 

 From these figures it is evident that the salts have lowered the freezing 

 point and the degree of this lowering is greater with the higher salt con- 

 tent present. After the temperature of all the different treatments 

 reached the freezing it remained there for some length of time, which 

 amount of time varied with the concentration : it was greatest for the 

 pure water and decreased with the increase in concentration of the 

 solution. This is an interesting fact and it is explained by the difference 

 in the further lowering of the freezing point due to the further increase 

 in concentration of the solution brought about by the separation of the 

 solidified solvent or ice under the subjection of the low temperature. 

 Finally, however, the temperature of the sand which received the differ- 

 ent densities of solution as well as the water, came to about the same 

 point, with a slight difference in favor of the solution treated with 

 sand. It is to be noted that the phenomenon of supercooling, such as 

 observed in the freezing of water in the form of drops or in capillary 

 tubes, also occurred in the freezing of soil water. It will be seen that 

 in almost every case some supercooling did take place. 



It will be interesting now to study the rate of thawing and rising of 

 temperature of the same lot of sands and see what relationship it has 

 to the rate of freezing. As already stated, this rate of thawing and 

 rising of temperature was measured by bringing the sands into the labor- 

 atory after their temperature was lowered to about the same point, and 

 records were taken every 10 minutes until their temperature was about 

 the same and close to the room temy)erature. The data thus obtained 

 are shown in table 88, and on the lower part of each chart. A glance 

 at these results reveals at once the significant fact that the rate of thaw- 

 ing was in every case, exactly the reverse of the rate of freezing. It 

 will be seen that the temperature of the sand treated with the water 

 rose at once to 31.8° F. or at the point in which solidification took place 

 and remained there for a long time until all the solid phase had been 

 converted over into the liquid phase and then it rose very rapidly. 

 While the temperature of the sand treated with the solutions rose at 

 the beginning slowly and gradually without remaining at any one point 

 for any length of time — which is just what should be expected since 

 fusion and solidification take place at the same point and since there 

 were more than one freezing point in the Case of these solutions on 

 account of their further concentration due to the separation of ice — 

 until complete fusion had taken place and then it rose very rapidly 

 and far above that of the sand treated Avith water. The rapidity with 



